| 摘要 |
<p>In the continuous prodn. of alkali aminopolyacetates (I) from HCHO and alkali cyanide (II) and opt. non-aromatic di- or tri-amine (III) in aq. soln. at elevated temp. 2 consecutive reaction zones, the ammonia (IV) formed in all reaction zones is removed continuously with an air stream, which is sucked through all zones at 15-150 (pref. 15-80) mbar below the ambient pressure in an amt. of 50-150 vol./mole (II) per hr. The process is simple, operates at only very slightly reduced pressure, and gives (I) with a low content of impurities, i.e. a colour value of 30-50 APHA, cf. 100-150 APHA obtd. in the discontinuous process. In an example, ethylene diamine, aq. NaCN and aq. HCHO soln. were passed through a cascade of 5 reactors, with addn. of more NaCN and HCHO in the second, third and fourth reactors. (IV) was removed with air at a pressure reduced by 65 mbar; 95-96% pure tetra-Na salt of EDTE was obtd. in the form of a 45% aq. soln., free from cyanide, with a colour value of 50 APHA.</p> |
